340 lines
8.6 KiB
Cheetah
340 lines
8.6 KiB
Cheetah
package {{.PackageName}}
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// The package is used as a template, don't use it directly!
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import (
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"fmt"
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"runtime"
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"sync"
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"time"
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)
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// Attr is cachmap attribute
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type {{.ValueType}}CacheAttr struct {
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// An (optional) function that is called with the key and value when an
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// item is evicted from the cache. (Including when it is deleted manually, but
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// not when it is overwritten.) Set to nil to disable.
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OnEvicted func(k string, v {{.ValueType}})
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DefaultCleanupInterval time.Duration // Default clean interval, this is a time interval to cleanup expired items
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DefaultExpiration time.Duration // Default expiration duration
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Size int64 // Initial size of map
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}
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// Item struct
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type Item struct {
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Object {{.ValueType}}
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Expiration int64
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}
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// Expired returns true if the item has expired.
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func (item Item) Expired() bool {
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return item.Expiration != 0 && time.Now().UnixNano() > item.Expiration
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}
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const (
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// NoExpiration is for use with functions that take no expiration time.
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NoExpiration time.Duration = -1
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// DefaultExpiration is for use with functions that take an
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// expiration time. Equivalent to passing in the same expiration
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// duration as was given to New() when the cache was
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// created (e.g. 5 minutes.)
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DefaultExpiration time.Duration = 0
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)
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// Cache struct
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type {{.ValueType}}Cache struct {
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*cache
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// If this is confusing, see the comment at the bottom of New()
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}
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type cache struct {
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defaultExpiration time.Duration
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items map[string]Item
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mu sync.RWMutex
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onEvicted func(string, {{.ValueType}})
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janitor *janitor
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}
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// Add an item to the cache, replacing any existing item. If the duration is 0
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// (DefaultExpiration), the cache's default expiration time is used. If it is -1
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// (NoExpiration), the item never expires.
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func (c *cache) Set(k string, x {{.ValueType}}, d time.Duration) {
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// "Inlining" of set
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var e int64
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if d == DefaultExpiration {
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d = c.defaultExpiration
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}
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if d > 0 {
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e = time.Now().Add(d).UnixNano()
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}
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c.mu.Lock()
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c.items[k] = Item{
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Object: x,
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Expiration: e,
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}
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// TODO: Calls to mu.Unlock are currently not deferred because defer
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// adds ~200 ns (as of go1.)
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c.mu.Unlock()
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}
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func (c *cache) set(k string, x {{.ValueType}}, d time.Duration) {
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var e int64
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if d == DefaultExpiration {
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d = c.defaultExpiration
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}
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if d > 0 {
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e = time.Now().Add(d).UnixNano()
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}
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c.items[k] = Item{
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Object: x,
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Expiration: e,
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}
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}
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// Add an item to the cache only if an item doesn't already exist for the given
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// key, or if the existing item has expired. Returns an error otherwise.
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func (c *cache) Add(k string, x {{.ValueType}}, d time.Duration) error {
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c.mu.Lock()
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_, found := c.get(k)
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if found {
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c.mu.Unlock()
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return fmt.Errorf("Item %s already exists", k)
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}
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c.set(k, x, d)
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c.mu.Unlock()
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return nil
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}
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// Set a new value for the cache key only if it already exists, and the existing
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// item hasn't expired. Returns an error otherwise.
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func (c *cache) Replace(k string, x {{.ValueType}}, d time.Duration) error {
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c.mu.Lock()
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_, found := c.get(k)
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if !found {
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c.mu.Unlock()
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return fmt.Errorf("Item %s doesn't exist", k)
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}
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c.set(k, x, d)
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c.mu.Unlock()
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return nil
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}
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// Get an item from the cache. Returns the item or nil, and a bool indicating
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// whether the key was found.
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func (c *cache) Get(k string) ({{.ValueType}}, bool) {
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c.mu.RLock()
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// "Inlining" of get and Expired
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item, found := c.items[k]
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// TODO: inline time.Now implementation
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if !found || item.Expiration > 0 && time.Now().UnixNano() > item.Expiration {
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c.mu.RUnlock()
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return {{.ValueType}}(0), false
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}
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c.mu.RUnlock()
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return item.Object, true
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}
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func (c *cache) get(k string) (*{{.ValueType}}, bool) {
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item, found := c.items[k]
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if !found || item.Expiration > 0 && time.Now().UnixNano() > item.Expiration {
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return nil, false
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}
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return &item.Object, true
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}
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{{ if call .IsNumberic .RealType }}
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// Increment an item of type int, int8, int16, int32, int64, uintptr, uint,
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// uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
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// item's value is not an integer, if it was not found, or if it is not
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// possible to increment it by n. To retrieve the incremented value, use one
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// of the specialized methods, e.g. IncrementInt64.
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func (c *cache) Increment(k string, n {{.ValueType}}) error {
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c.mu.Lock()
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v, found := c.items[k]
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if !found || v.Expired() {
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c.mu.Unlock()
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return fmt.Errorf("Item %s not found", k)
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}
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v.Object += n
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c.items[k] = v
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c.mu.Unlock()
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return nil
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}
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// Decrement an item of type int, int8, int16, int32, int64, uintptr, uint,
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// uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
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// item's value is not an integer, if it was not found, or if it is not
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// possible to decrement it by n. To retrieve the decremented value, use one
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// of the specialized methods, e.g. DecrementInt64.
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func (c *cache) Decrement(k string, n {{.ValueType}}) error {
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// TODO: Implement Increment and Decrement more cleanly.
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// (Cannot do Increment(k, n*-1) for uints.)
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c.mu.Lock()
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v, found := c.items[k]
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if !found || v.Expired() {
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c.mu.Unlock()
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return fmt.Errorf("Item not found")
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}
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c.items[k] = v
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c.mu.Unlock()
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return nil
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}
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{{end}}
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// Delete an item from the cache. Does nothing if the key is not in the cache.
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func (c *cache) Delete(k string) {
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// fast path
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if c.onEvicted == nil {
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c.mu.Lock()
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c.deleteFast(k)
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c.mu.Unlock()
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return
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}
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// slow path
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c.mu.Lock()
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v, evicted := c.delete(k)
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c.mu.Unlock()
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if evicted {
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c.onEvicted(k, v)
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}
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}
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func (c *cache) delete(k string) ({{.ValueType}}, bool) {
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if v, found := c.items[k]; found {
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delete(c.items, k)
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return v.Object, true
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}
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//TODO: zeroValue
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return 0, false
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}
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func (c *cache) deleteFast(k string) {
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delete(c.items, k)
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}
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type keyAndValue struct {
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key string
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value {{.ValueType}}
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}
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// Delete all expired items from the cache.
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func (c *cache) DeleteExpired() {
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var evictedItems []keyAndValue
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now := time.Now().UnixNano()
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// fast path
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if c.onEvicted == nil {
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c.mu.Lock()
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for k, v := range c.items {
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// "Inlining" of expired
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if v.Expiration > 0 && now > v.Expiration {
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c.deleteFast(k)
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}
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}
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c.mu.Unlock()
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return
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}
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// slow path
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c.mu.Lock()
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for k, v := range c.items {
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// "Inlining" of expired
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if v.Expiration > 0 && now > v.Expiration {
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ov, evicted := c.delete(k)
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if evicted {
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evictedItems = append(evictedItems, keyAndValue{k, ov})
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}
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}
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}
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c.mu.Unlock()
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for _, v := range evictedItems {
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c.onEvicted(v.key, v.value)
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}
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}
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// Returns the number of items in the cache. This may include items that have
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// expired, but have not yet been cleaned up. Equivalent to len(c.Items()).
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func (c *cache) ItemCount() int {
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c.mu.RLock()
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n := len(c.items)
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c.mu.RUnlock()
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return n
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}
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// Delete all items from the cache.
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func (c *cache) Flush() {
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c.mu.Lock()
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c.items = map[string]Item{}
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c.mu.Unlock()
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}
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type janitor struct {
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Interval time.Duration
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stop chan bool
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}
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func (j *janitor) Run(c *cache) {
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j.stop = make(chan bool)
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ticker := time.NewTicker(j.Interval)
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for {
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select {
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case <-ticker.C:
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c.DeleteExpired()
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case <-j.stop:
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ticker.Stop()
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return
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}
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}
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}
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func stopJanitor(c *{{.ValueType}}Cache) {
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c.janitor.stop <- true
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}
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func runJanitor(c *cache, ci time.Duration) {
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j := &janitor{
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Interval: ci,
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}
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c.janitor = j
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go j.Run(c)
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}
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func newCache(de time.Duration, m map[string]Item) *cache {
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if de == 0 {
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de = -1
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}
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c := &cache{
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defaultExpiration: de,
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items: m,
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}
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return c
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}
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func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]Item, onEvicted func(k string, v {{.ValueType}})) *{{.ValueType}}Cache {
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c := newCache(de, m)
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c.onEvicted = onEvicted
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// This trick ensures that the janitor goroutine (which--granted it
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// was enabled--is running DeleteExpired on c forever) does not keep
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// the returned C object from being garbage collected. When it is
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// garbage collected, the finalizer stops the janitor goroutine, after
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// which c can be collected.
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C := &{{.ValueType}}Cache{c}
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if ci > 0 {
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runJanitor(c, ci)
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runtime.SetFinalizer(C, stopJanitor)
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}
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return C
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}
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// New Returns a new cache with a given default expiration duration and
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// cleanup interval. If the expiration duration is less than one
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// (or NoExpiration), the items in the cache never expire (by default),
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// and must be deleted manually. If the cleanup interval is less than one,
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// expired items are not deleted from the cache before calling c.DeleteExpired().
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//
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func New{{.ValueType}}Cache(attr {{.ValueType}}CacheAttr) *{{.ValueType}}Cache {
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items := make(map[string]Item, attr.Size)
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return newCacheWithJanitor(attr.DefaultExpiration, attr.DefaultCleanupInterval, items, attr.OnEvicted)
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}
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